Fluorescent screen



Jain. 2, 1962 a. ROSENBERG FLUORESCENT SCREEN Filed June 19, 1959Radiation Source Volloge Controllable Fluorescent Solution Video JSource X Scan Generator Sync Separator Y Scan Generator United StatesPatent 3,0l5,747 FLUORESCENT SCREEN Barnett Rosenberg, New York. N.Y.,assign' r to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Filed June 19, 1959, Ser. No. 821,510 6Claims. (Cl. 313-108) This invention relates to a fluorescent screen,and more particularly to a fluorescent screen for the production ofcolor images. I

It has been known for some time that certain materials will exhibitfluorescence in aqueous solutions over a limited range of pH values(i.e. hydrogen ion concentration), when excited by electromagneticradiation such as ultra violet. These materials are presently being usedas indicators to determine the pH of solutions and also in chemicalanalysis procedures to adjust the pH of a solution to a desired value.In these procedures a small quantity of such an indicator is added to asolution, the pH of which is to be adjusted. The indicator added isgenerally in a fluorescent state at the pH desired and in anon-fluorescent state at all other pH values. The solution is positionedso that electromagnetic radiation such as ultra violet is incidentthereon and either an acid or a base is slowly added until the solutionfluoresces. At this point the pH is that at which the indicator is knownto change from the non-fluorescent to the fluorescent state. Thesematerials are especially adapted to be used in imaging display devicesbecause of the quantum efliciency of fluorescence. That is, the energyoutput comes close to the energy input. Further by a proper choice ofthe indicator any desired fluorescent color can be obtained.

For use as an imaging device it is necessary to alter the pH of thesolution independently over elementary areas of the solution. This canbe accomplished by providing a grid like structure of conductors oneither side of the solution. By impressing an electric field gradientacross the solution a charge migration will result and a largeconcentration of negative ions will surround the positive electrode anda large concentration of positive ions will surround the negativeelectrode, thus changing the pH over an elemental area. The indicatorchosen will be such that it is in the non-fluorescent state when nofield is applied and in the fluorescent state when a field is appliedacross the solution.

By the use of an electrode system that will provide a plurality ofcontinuing paths through the solution, a cell member containing such asolution may be utilized as an imaging display device.

lt is, therefore, an object of this invention to provide an improvedimage display device.

Another object is to provide a colored i'naging display device.

A further object is to provide an improved imaging display device thatmay be viewed in ordinary light.

An auxiliary object is to provide an improved imaging display deviceutilizing a material which exhibits a body color change upon a change inhydrogen ion concentration.

An additional object is to provide an improved imaging display devicehaving good definition and brightness characteristics.

A supplementary object is to provide an improved imaging display deviceutilizing fluorescent indicators.

These and other objects of this invention will be ap parent from thefollowing description taken in accordance with the accompanying drawingthroughout which, like reference characters indicate like parts whichdrawing forms a part of this application in which:

FIGURE. 1 is a cutaway perspective view of a mono- Patented Jan. 2, 1962ICC 2 color image display device in accordance with this invention,

FIG. 2 is a cross-sectional view of a tricolor image display device inaccordance with this invention, and;

FIG. 3 is an exploded perspective view of the embodiment shown in FIG.2, together with associated circuitry.

In FIG. 1, there is illustrated a cutaway perspective view of amonocolor image display device comprising a single cell member 11. Thecell member Includes a first support member 13 transmissive toelectromagnetic radiation, such as glass. The support member 13 isprovided with a first grid member 15 comprising a plurality ofelectrically conducting members 17 which are arranged in a parallelfashion. Adjacent the conducting member 15 is disposed a voltagecontrollable fluorescent solution 19. That is a solution which willchange from a non-fluorescent state to a fluorescent state upon theapplication of a voltage across the solution. It is to be understoodthat in this application including the claims the term solutionincludes, but is not limited to liquid solutions, solid solutions,colloids, sols. suspensions, gels, suspended particles in a generallywide range of sizes and materials impregnated with a synthetic resin.

An example of such a solution may be made by dissolving a suitablefluorescent indicator such as brilliant diazo yellow, chromotropic acid,Cleves acid, coumaric acid, dichlorofluorescein, eosin, eosin. yellow,eosin BN porphyn'n and other materials which will exhibit fluorescenceupon a change in the hydrogen ion concentration in a water, alcohol orglycerine solvent. To this solution is added a small quantity of ahighly ionized salt, such as potassium chloride, sodium chloride, sodiumfluoride, sodium sulfate and other such salts of this class. Those saltsare to be used which have no quenching efiect on the solutionfluorescence. The solvent chosen to dissolve the organic dye should bemiscible with water to guarantee the complete solution of the watersoluble indicator and salts. If it is desirable gelatin may be added toform a gel of the solution. The pH of the solution is then adjusted tothat value at which the indicator will be in the non-fluorescent state.

On the opposing side of the solution 19, with respect to the firstsupport member 13, is disposed a second support member 21 having asecond grid member 23 of parallel conductors 25. ConductorsZS aredisposed at an angle with respect to the conductors 17 on the firstsupport member 13, so that projections of both grid members 15 and 23form an intersecting pattern. It is preferable that the conductors 17 onthe fi'st support ember 13 be at ri ht angles with the conductors 25 onthe second support member 21 but any angle will operate satisfactorily.A source of electromagnetic radiation 27, such as ultra violet light,may be positioned around the cell structure 11 or may be spaced from thecell structure 11 in such a manner that the rad'ation is in dmt upon thevoltage controlled fluorescent solution 19.

The conductors 17 and 25 may also be covered with an insulating layer(not shown) to prevent electrolytic action at the electrodes. Of course,if the voltage controlled fluorescent solution 19 is a liquid, thevolume between the support members should be made liquid tight bysealing the support members together around their periphery by asuitable insulating material, such as g'ass.

In operation, a video signal would be impressed on one of the conductors17 and 25 of each grid member in accordance with the incominginformation bearing signal. At the point where the two conductors crossthe ions in the voltage controlled fluorescent solution 19 will migratetoward the conductors 17 and 25 caus'ng a change in the hydrogen ionconcentration of the solution over a small elemental area of the entirecell memher 11. Upon the incidence of ultra violet radiation, this pointwill be the only point to emit visible light since the remainder of thesolution in the cell 11 has not been altered from its non-fluorescentstate. In this manner, an image could be produced by applying a timesequential information bearing signal to the conductors 17 and 25. Theassociated circuitry shown is one means by which an information bearingsignal could be distributed so as to form a visible image.

As shown in FIG. 1, the video signal is derived from a video signalsource which may be a video information bearing signal from the videoamplifier of a conventional television receiver circuit. Synchronizinginform'ttion is derived from the video signal in the sync separator 12.The sync signal is resolved into X and Y components in the X scangenerator 14 and the Y scan generator 16 and applied to the Xdistributor 18 and the Y distributor 20 respectively. The distributors18 and 20 have a plurality of output circuits 22 and 24 for sequentialapplication of the switching pulses to the conductors 17 and 25respectively. The distributors 18 and 20 may comprise pulse delay linesconstructed in accordance with practices Well known in the art and theremay be other types as described in copending application Serial No.747,799 entitled Signal Distribution System, by Francis T. Thompson,filed July 10, 1958, and assigned to the same assignee.

The inelligence signalfrom the video source 10 is fed directly to the Xdistributor 18 and through a phase inverter 26, to reverse the polarity,to the Y distributor 20. These information bearing signals are appliedsequentially in accordance with the scanning rate to produce an image oncell member 11.

The conductors 17 and 25 may be made by evaporating metallic materialsonto a glass plate and then ruling away a portion to form parallelconductors. Another method would be to evaporate a metallic materialthrough a masking pattern. The conductors 17 and 25, if made of ametallic material. should be a thin layer which would not render theconductors opaque. Metallic materials that may be used for theconductors 17 and 25 include: aluminum, cadmium, platinum, nickel andsilver. The conductors 17 and 25 also may be a coating of tin oxide.Conductors of tin oxide may be made by sprayin a solution of stannicchloride onto the glass support members 13 and 21 which have been heatedto a temperature of approximately 600 C. To prevent electrolytic actionat the conductors 17 and 25, they may be coated with a thin layer ofinsulating material such as polyethylene or nylon.

A specific example of the solution used in the cell memb r 11 mav be madbv dissolving one gram of dichlorofluorescein in alcohol, such as amethyl, ethyl, butyl type of alcohol or any other alcohol which ismiscible with water. This solution of the dichlorofluorescein in alcoholis then admixed with one liter of water. To this solution is added 50 to100 grams of sodium chloride. The solution is then adjusted to a pHvalue of below 4. In this condition, the solution is in thenon-fluorescent state. When the pH is changed by any means to the rangeof 4 to 6, the solution is rendered florescent and will emit light inthe green region of the spectrum upon the incidence of ultra violetlight. For optimum light output the cell member should be approximately.(l04 inch thick but for varied uses it may be between .0005 inch and.008 inch.

FIG. 2 shows an arrangement wherein a series of three cells 35, 37 and39, as described in FIG. 1, are arranged in a parallel adjacentrelationship. By this arrangement, each cell may contain a dilterentvoltage controlled fluorescent solution which emits in the red, greenand blue regions of the visible spectrum, to obtain a colored imagingdevice. A material which will undergo a change from the non-fluorescentstate to a fluorescent state in the red region of the spectrum isporphyrin. This material is non-fluorescent in alkali solution andfluorescent in acid solution. A solution which will undergo a changefrom the non-florescent state to a fluorescent state in the blue regionof the spectrum is chromotropic acid. This acid will be fluorescent at apH of 3.5 to 4.5 and non-florescent at other pHs. A solution which willundergo a change from the nonfluorescent state to a fluorescent state inthe green region of the spectrum is coumaric acid ordichlorofluorcscein. Coumaric acid undergoes a change fromnon-fluorescent to the fluorescent state when a change in the pH occursto 6 to 8, while dichlorofluorescein undergoes a change from thenon-fluorescent to the fluorescent state by a change in pH to 4 to 6.The conductors of each of the cell members are in registry so that bycolor addition any elemental area may appear to the eye to have anycolor of the visible spectrum.

Each cell member 35, 37 and 39 is identical with the exception that eachcell contains a different solution. For example cell 35 may containporphyrin which will fluoresce in the red. Cell 37 may containchromotropie acid which will fluoresce in the blue and cell 39 maycontain coumaric acid which will fluoresce in the green.

As shown in FIG. 2, cell member 35 includes support member 36 havingconductors 38 disposed thereon, a voltage controlled solution 41 andsupport member 43 having conductors 45 disposed thereon. Cell member 37includes support member 43, which is common to both cell members 35 and37, and has disposed thereon conductors 47 on the side opposed to thaton which conductors 45 are located. The cell member 37 also includes avoltage controlled solution 49 and a second support member 51 havingconductors 53 disposed there on. Cell member 39 includes support member51, which is common to both cell members 37 and 39. Conductors 55 aredisposed on the surface of support member 51 opposed to the surface onwhich conductors 53 are located. The cell member 39 also includes avoltage controlled solution 57 and a second support member 59 havingdisposed thereon conductors 61. The solutions are contained within eachof the cell members 35, 37 and 39 by the envelope 63 which makes aliquid tight joint with support members 36, 43, 51 and 59 around theirperiphery. The adjacent cell members may have common support members asshown in FIG. 2, or they may be a series of stacked individual cellsarranged in parallel adjacent relationship.

In FIG. 3 there is shown an exploded view of a series of cell members35, 37 and 39 arranged for color rendition. The cells may be as shown inFIG. 2 or they may be a series of individual cells, each containing adifferent solution-and arranged in a stacked relationship.

The circuit for the application of intelligence signals to the cells issubstantially the same as that shown in FIG. 1 with the exception that asynchronous demodulation means 40 is included between the video source10 and the phase inverter 26 to separate the red, green and blue colorsignals. The phase inverters and X and Y distributors for the green andblue signals have been omitted for the purpose of simplicity but thisportion of each circuit may be identical with that shown for the redsignal with the exception that the output circuits of the distributorswould be connected to cells 37 and 39. As can be seen in FIGS. 2 and 3the conductors of each cell are in registry, therefore by applying timesequential signals to each cell simultaneously, the image produced willappear to the viewer to be a colored replica of the scene beingreproduced.

In some instances, it may be desirable to utilize materials whichundergo a body change in color, instead of a change from anon-fluorescent to a fluorescent state. In such an example, the color ofan elemental area would he arrived at by the subtractive method. In suchan instance, the solution of each cell would contain a material whichundergoes a color change from colorless to red, blue and yellow. Table Ilists examples of materials that exhibit these properties together withthe pH range and the color of each in the colored and colorless state.

In such an embodiment as this, the ultra violet source 27 would beremoved and a source of white light would be placed on the side of thecell structure opposite to the viewing side. This may take the form of awhite emitting electroluminescent plate.

The dyes should have narrow absorption bands in the spectral regions.The color the dye takes when activated must be that of white light minusthe region it absorbs. Thus for a black point on the picture, all threelayers must be activated by a voltage pulse. For a white point on thepicture no layers are activated. For a red signal the two layers thattransmit red but absorb the blue and yellow are activated.

A specific embodiment of a single cell structure would have a totalthickness of approximately 0.25 inch the thickness of the conductorswould be 0.245 inch and the thickness of the voltage controlled solutionwould be 0.005 inch.

Such a system as described herein would find application in devices sucha panel TV, plotting boards and panel displaying systems. In all ofthese systems, the desideratum is to control the light output, that is,intensity or color from an element of area of a broad area surface inproportion to some electrical or optical signal on that area. By the useof the voltage controlled fluorescent solutions as described herein, itis believed that many of the disadvantages which are found in thecurrent devices, such as a need to reduce the ambient light surroundingthe particular device, are eliminated.

While the present invention has been shown in several forms only, itwill be obvious to those skilled in the art that it is not so limited,but is susceptible of various changes and modifications withoutdeparting from the spirit and scope thereof.

I claim as my invention:

1. A color imaging screen comprising a plurality of cell membersarranged in parallel relationship, each of said cell members including asolution capable of being transformed from a non-fluorescent to afluorescent state upon a change of the hydrogen ion concentration ofsaid solution, each of said cells having a different characteristicemission wavelength, a source of electromagnetic radiation positioned soas to irradiate said plurality of cells and a means for changing thehydrogen ion concentration of discrete elemental areas of said cellmembers.

2. -A color imaging screen comprising a plurality of cell membersarranged in parallel relationship, each of said 5 cell members includinga solution capable of being transformed from a non-fluorescent to afluorescent state upon a change of the hydrogen ion concentration ofsaid solution, each of said cells having a different characteristicemission wavelength, at source of electromagnetic radi- 7o ationpositioned so as to irradiate said plurality of cells and a means forchanging the hydrogen ion concentration of discrete elemental areas ofsaid cell members, said means including a series of conductors on eitherside of each cell member so that projections of each form anintersecting pattern.

3. A color imaging screen comprising, a plurality of cell membersarranged in parallel relationship, each of said cell members including asolution capable of being transformed from a non-fluorescent to afluorescent state upon a change of the hydrogen ion concentration ofsaid solution, each of said-cells having a different characteristicemission wavelength, a source of electromagnetic radiation positioned soas to irradiate said plurality of cells and a means for changing thehydrogen ion concentration of discrete elemental areas of said cellmembers. said means including a pair of grid members associated witheach of said cell members, said pair of grid members including a firstgrid member and a seeond grid member, said first grid member of eachpair being disposed on one side of said associated cell member andincluding a plurality of parallel spaced conductors, the second gridmember of each pair being disposed on the opposing side of saidassociated cell member and including a plurality of parallel spacedconductors being substantially at right angles to said conductors ofsaid first grid member so that projections of both grid members form anintersecting pattern.

4. Ala imaging screen comprising a cell member including a solutioncapable of being transformed from a nonfluorescent to a fluorescentstate upon a change of the hydrogen ion concentration of said solution,said solution comprising a solvent. a readily ionizable salt and amaterial selected from the group consisting of diazo yellow,chromotropic acid, Cleves acid, coumaric acid. dichlorofiuorescein,eosin, eosin yellow and eosin BN porphyrin, a. source of electromagneticradiation positioned so as to irradiate said cell and meansfor changingthe hydrogen ion concentration of discrete elemental areas of said cell.

5. .An imaging screen comprising a cell member including a solutioncapable of being transformed from a nonfluorescent to a fluorescentstate upon a change ofthe hydrogen ion concentration of said solution,said solution consisting essentially of a quantity ofdiehlorofiuorescein, a quantity of water-miscible alcohol sufficient todissolve said dichlorofiuorescein and, for each gram of saiddichlorofiuorescein, 50 to grams of sodium chloride and one liter ofwater, a source of ultraviolet light positioned so as to irradiate saidcell member and a means for changing the hydrogen ion concentration ofdiscrete elemental areas of said cell member.

6. A color imaging screen comprising three cell members arranged inparallel relationship, each of said cell members including a solutioncapable of being trans-' formed from a non-fluorescent to a fluorescentstate upon a change of the hydrogen ion concentration of said solution,a first of said cell members having a quantity of porphyrin in thesolution therein, a second of said cell members having a quantity ofchromotropic acid in the solution therein and a third of said cellmembers having a quantity of a material selected from the groupconsisting of coumaric acid and dichlorofluorescein, a source ofelectromagnetic radiation positioned so as to irradiate said pluralityof cell members and means for changing the hydrogen ion concentration ofdiscrete elemental areas of said cell members.

References Cited in the file of this patent Proceedings of the IRE, vol.43, No. 12, December 1955, pages 1911 to 1940.

Electronic Industries and Tele-Tech, February 1957, pages 51 to 53,

1. A COLOR IMAGING SCREEN COMPRISING A PLURALITY OF CELL MEMBERSARRANGED IN PARALLEL RELATIONSHIP, EACH OF SAID CELL MEMBERS INCLUDING ASOLUTION CAPABLE OF BEING TRANSFORMED A NON-FLUORSECENT TO A FLUORESCENTSTATE UPON A CHANGE OF THE HYDROGEN ION CONCENTRATION OF SAID SOLUTION,EACH OF SAID CELLS HAVING A DIFFERENT CHARACTERISTIC EMISSION WAVELENGHTA SOURCE OF ELECTROMAGNETIC RADI-